Dissimilar thermal transport properties in κ-Ga2O3 and β-Ga2O3 revealed by homogeneous nonequilibrium molecular dynamics simulations using machine-learned potentials.

The lattice thermal conductivity (LTC) of Ga 2 O 3 is an important property due to the challenge in the thermal management of high-power devices. In this work, we develop machine-learned neuroevolution potentials (NEPs) for single-crystalline β - Ga 2 O 3 and κ - Ga 2 O 3 and demonstrate their accuracy in modeling thermal transport properties. Combining NEP-driven homogeneous non-equilibrium molecular dynamics simulations with tensor analysis, we determine the spatial distributions of LTCs for two Ga 2 O 3 crystals, showing dissimilar thermal behaviors. Specifically, β - Ga 2 O 3 shows isotropic thermal transport properties, with the LTCs along [100], [010], and [001] directions being predicted to be 10.3 ± 0.2 , 19.9 ± 0.2 , and 12.6 ± 0.2 W/(m K), respectively, consistent with previous experimental measurements. For κ - Ga 2 O 3 , our predictions suggest nearly isotropic thermal transport properties, with the LTCs along [100], [010], and [001] being estimated to be 4.5 ± 0.1 , 3.9 ± 0.1 , and 4.0 ± 0.1 W/(m K). The reduced LTC of κ -Ga 2 O 3 vs β -Ga 2 O 3 stems from its restricted low-frequency phonons up to 5 THz. Furthermore, we find that the β phase exhibits a typical temperature dependence slightly stronger than ∼ T − 1 , whereas the κ phase shows a weaker temperature dependence, ranging from ∼ T − 0.5 to ∼ T − 0.7 . [ABSTRACT FROM AUTHOR]